Inorg. Chem. 1982, 21, 4166-4169
4166
Contribution from the Istituto per lo Studio della Stereochimica ed Energetica dei Composti di Coordinazione del CNR, Florence, Italy
Chemistry of Et3P*CS2Metal Complexes: Synthesis of 1,l-Dithiolate Complexes via Nucleophilic Attacks on [(triphos)Co(S2CPEt3)](BPh4)2.X-ray Structure of [(triphos)Co(S2CO)] C. BIANCHINI,* A, MELI, and A, ORLANDINI
Recetved Aprll 16, 1982
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The synthesis of the 1,l.dithiolate cobalt(I1) complexes [(triphos)Co(SaC(H)PEt3)]BPh4 (2), [(triphos)Co(S&O)] (3), and [(triphos)Co(SaCS)] (4) (triphos l,l,l~tris((diphenylphosphino)methyl)ethano) via the reaction of complex [ (triphos)Co(S2CPEt3)](BPh4)a (1) with nucleophiler has been described. All the complexes have been characterized by appropriate physical methods. The molecular structure of 3 has been determined from counter diffraction data, Crystal data for 3: u 20.294 (8) A, 6 = 17,954 (7) A,c 10.218 (4) A, orthorhombic, space group PnZlu,Z = 4. The stucture was refined by full-matrix least-squares techniques to R and R, of 0,063 and 0.055, respectively, The cobalt atom is five-coordinated by the three phosphorus atoms of the triphos ligand and by the two sulfur atoms of the dithiocarbonate group in a distorted-square-pyramidal environment.
-
-
Introduction In recent papers the coordinative behavior of the triethylphosphintcarbon disulfide adduct, Et3PCSz,has bcen widely Indeed this molecule exhibits various anchoring modes to metals, behaving as an VI,q2, or q3 ligand (Figure 1).
Among the complexes obtained, those containing the zwitterion Et3P*CS2as a bidentate ligand, have aroused our interest since a metal ion, when chelated, often causes the electrons in a ligand to be redistributed, and as a result, the reactivity at some point in the chelate ring is altered to some extent, On the other hand it has been extensively reported that dithio acid metal complexes such as xanthates, dithiocarbamates, and trithiocarbonates may undergo nucleophilic attack on the carbon atom of the -CS2 group,**' With this in mind, we have investigated the reactivity of the complex [ (triphos)C~(S~CPEt~)](BPh~)~ (1) (triphos = 1,1,l-tris((dipheny1phosphino)methyl)ethane) toward various nucleophiles. The reactions performed are summarized in Scheme I; some of them represent a novel and potentially useful route to metal complexes with ligands such as S2C02' and S,C(H)PEt,-, which do not exist in the free form, All complexes have been characterized and their physical properties studied by the usual methods, A complete X-ray structure determination has been carried out on the complex [ (triphos)Co(S2CO)] (3). A preliminary account of part of this work has already been published.* Experimental Section Compound 1 was prepared according to a published procedure.* Tetrahydrofuran was dried by refluxing over LiA1H4,before distillation. All other chemicals and organic solvents employed were reagent grade and were used without further purification. Preparation of the Complexes. All reactions were routinely performed in an atmosphere of dry nitrogen except where stated otherwise. (1) Bianchini, C.; Ghilardi, C. A.; Meli, A,; Midollini, S.; Orlandini, A, Organometalllcs 1982, I, 778. (2) Bianchini, C.; Ghilardi, C. A,; Meli, A,; Midollini, S.; Orlandini, A. J . Organomet. Chem, 1981, 219, C13. (3) Bianchini, C.; Meli, A.; Orlandini, A,; Scapacci, G.J . Organomet. Chem. 1981, 215, C59. (4) Bianchini, C.; Innwenti, P.; Meli, A,; Orlandini, A,; Scapacci, G. J . Organomet. Chem. 1982, 233, 233. (5) Bianchini, C.; Meli, A.; Orlandini, A. Inorg. Chem., in press. (6) Facklcr, J. P., Jr.; Scidel, W. C. Inorg. Chem. 1969, 8, 1631. (7) Bianchini, C.; Mealli, C.;Meli, A,; Scapacci, G. J . Chem. SOC.Dalton Trans. 1982, 799. (8) Bianchini, C.; Meli, A,; Orlandini, A. Angew. Chem. Suppl. 1982,471.
0020-1669/82/ 1321-4166$01.25/0
The solid complexa were collected on a sintered-glass frit and washed sucoessively with ethanol and petroleum ether (bp 40-70 "C) before being dried in a stream of dry nitrogen, [(Mphor)Co(S2C(H)PEt3)]BPb, (2), A solution of NaBH, (0.7 "01) in ethanol (20 mL) waa added to a susponsion of 1 (0.5 mmol) in CHaCla (30 mL), The suspended solid dissolved to give an orangbbrown solution. Orangbbrown crystals were obtained on addition of ethanol and slow evaporation of the mlvent, They were recrystallized from acetone and butanol. Conductivity: 45 Q-l cmz mol". Anal. Calcd for C7aH7,BCoP4Sa: C, 72,17; HI 6,31; Co, 4,91; P, 1034. Found: C, 72,02; H, 6,26; Co, 4,83; PI 10,31, [(triphor)Co(S2CO)](3). Sodium metal (2 mmol) was allowed to react completely with 20 mL of ethanol, and the resulting solution of sodium ethoxide was slowly added to a suspension of 1 (03mmol) in THF (30 mL) until it dissolved to give a red-violet solution. Dioxygen was then bubbled until the color changed to yellow-green. After concentration of the resulting solution, yellow-green crystals wore obtained, which were reorystallized from CHaClaand ethanol. 3 can also be obtained by exposing a CHaCla/ethanol solution of 2 to the air, Anal. Calcd for C41H39C~OP3SZ: C, 65.02; H, 5.06; Co, 7S9. Found: C, 64,97; HI 5.03; Co, 7 3 , [(Mphor)Co(SaCS)] (4), A solution of sodium ethoxide, prepared as above, was slowly added to a susponsion of 1 ( 0 3 mmol) in THF (30 mL) until complete dissolution. A large excea of sulfur in boiling THF (20 mL) was then added, On addition of butanol (20 mL), red crystals precipitate, which were recrystallized from CHaCll and butanol, Anal, Calcd for CgH3&oP3S3: C, 63.70; HI 4,96; Co, 7.44; SI 12.14. Found: C, 63.72; H, 4.93; Co, 7.40; SI 12,09. [(Mphor)Co(~-C&)] (5). A suspension of 1 (0.3 "01) and sodium sand (1.5 mmol) in THF (30 mL) was stirred at room temperature until a deep red solution was obtained (about 2 h) and then stirred for a further 30 min. Butanol (20 mL) was then added to the filtered solution, Dark red crystals formed on standing, Physical Meiw"enQ. Infrared spectra were obtained as Nujol mull with a Perkin-Elmer 283 apsctrophotometer, The methods used for the magnetic measurements and the recording of the UV-visible spectra have been described previously? Conductance measurements were made with a WTW Model LBR/B conductivity bridge in ca. 10-3 M nitroethane solutions. Collectionand Reduction of X-ray Intensity Data. A yellow-green prism of approximate dimensions 0.1 X 0.2 X 0.3 mm was selected for data collection on a Philips PW 1100 diffractometer, by using Mo Ka (A = 0.7107 A) graphite-monochromated radiation. The crystals are orthorhombic and belong to space group PnZla, as inferred from the systematic absences Okl for k I = 2n + 1 and hkO for h = 2n 1, with four molecules in the unit cell. Cell dimensions, determined by least-squares refinement of the angular settings of 20 carefully centered reflections, are u = 20.294 (8) A, b = 17.954 (7) A, c = 10.218 (4) A, and V = 3723.0 A3, The calculated density is 1.384 g cm-3 for Z = 4. For the intensity collection an 0-28 scan
+
+
(9) Sacconi, L.; Bertini, I.; Mani, F. Inorg. Chem. 1968, 7 , 1417.
0 1982 American Chemical Society
Inorganic Chemistry, Vol. 21, No. 12, 1982 4167
Structure of [(triphos)Co(S2CO)] Scheme I 1 N
5 rc/
4
3
2
/v
Y
Iv
Table I. Positional and Thermal Parameters for [(triphos)CoS,CO]" atom co P1
X
Y
Z
UI I
u 1 2
u 3 3
UIZ
1'
3
u 23
-527 (2) -1321 474 (3) 33 (2) 25 (2) 40(2) 3 (3) 4 (2) -7 (2) 539 (3) -1266 (4) 1060 (5) 32 (3) 30 (3) 43 (4) -6 (4) -4 (4) 3 (4) P2 -428 (3) -178 (3) -427 (7) 35 (4) 25 (3) 47 (5) 1(4) 8 (5) -1 (3) P3 -850 (3) -829 (4) 2418 (8) 24 (3) 37 (3) 35 (4) -6 (4) 4 (4) -3 (3) S1 -1509(3) -1616 (4) -430 (9) 45 (4) 96 (6) -12 ( 5 ) -40 (5) 1(3) 53 (4) s2 -546 (4) -2574 (4) 473 (10) 51 (5) 32 (4) -9 (8) -20 (4) 170 (10) -7 (6) " The form of the thermal ellipsoid is exp[-2n2(U,,h2a*' + U21kzb*2+ U3312c*2+ 2UlZhka*b*+ 2UI3hla*c*+ 2U2,klb*c*)]. Coordinates are multiplied by lo4;temperature factors, by lo3. They coordinate of the Co atom was chosen to have accordance with the isomorphous [ (triphos)Co(BH,)] complex.'
Figure 1.
mode was used with a scan width variable with 8, according to the expression A + B tan 8, where A = 0.8O and B = 0.69. A scan speed of O.O6O/s was used. Background counts were made for half of the scan time at each end of the scan. Three control reflections were monitored every 120 min, but no systematic trend was noticed. After correction for background, the standard deviations u(0 of the intensity I were calculated as previously described1° by using the value of 0.03 for the instability factor k. Intensity data were corrected for Lorentz and polarization effects, but no absorption correction was applied, o = 7.26 cm-I. An the linear absorption coefficient being ~ ( M Ka) empirical estimation of the effect of absorption showed the largest change in intensities within 2%. From a total of 2895 reflections ( 5 O < 20 C 4 6 O ) , 1070 were considered observed with I > 2.50(0. Atomic scattering factors of the neutral atoms were taken from ref 11 for non-hydrogen atoms and from ref 12 for hydrogen atoms. Both the Af' and Aj" components of anomalous dispersion were included for all non-hydrogen atoms.13 The function minimized during the least-squares refinement was Cw(lFol - IFcl)z,where w are given as w = I / U ( F , ) ~All . calculations were carried out by using SHELX-76 crystallographic system, on a SEL 32/70 computer installed in our institute.14 Solution and Refiiment of the Structure. On the assumption that the compound is isomorphous with [ ( t r i p h o s ) C ~ ( B H ~ the ) ] , ~final ~ parameters of this structure were used as starting parameters of the present complex. A A F Fourier revealed the positions of the SzCO (10)
Corfield, P. W. R.; Doedens, R. J.; Ibers, J. A. Inorg. Chem. 1967,6,
group. Full-matrix least-squares cycles, by assigning isotropic temperature factors to all the non-hydrogen atoms, were followed by mixed cycles, where anisotropic temperature factors were attributed to cobalt, sulfur, and phosphorus atoms. Throughout the refinement the phenyl rings were treated as rigid bodies of D6h symmetry. At this point the hydrogen atoms were introduced in their calculated positions but were not refined. Owing to the polar nature of the Pn2,a space group, two possible orientations of the structure (x, y , z ) and (x, j j , z ) are to be considered. The absolute configuration was determined by applying the anomalous dispersion corrections. A final least-squares cycle led to convergence at the discrepancy factors R = 0.063 and R, = 0.055 for (x, y , z ) and R = 0.064 and R, = 0.057 for (x, j j , z ) , respectively. An analysis of the standard deviations confirmed that the (x, y, z ) structure was the correct one. Tables I and I1 report the final positional and thermal parameters with their estimated standard deviations for all non-hydrogen atoms. A listing of F, and F, structure factors is available as supplementary material.
Results and Discussion It has been recently reported that the C 1 carbon atom of 1 has so much electrophilicity as to be able to abstract a
1
hydride ion from ethan01.~This finding has prompted us to investigate the reactivity of the coordinated Et3P.CS, ligand toward various nucleophiles. Indeed hydride ion attacks the C 1 carbon atoms: by reaction of BH4- anions with 1, the cobalt(I1) derivative [(triphos)Co(S2C(H)PEt3)]BPh4 (2) is easily p r e ~ a r e d.. ~
1979 .. .
"International Tables for X-Ray Crystallography"; Kynoch Press: Birmingham, England, 1974; Vol. IV, p 99. Stewart, R. F.;Davidson, E. R.; Simpon, W. T. J . Chem. Phys. 1965, 42, 3175.
'International Tables for X-Ray Crystallography"; Kynoch Press: Birmingham, England, 1974; Vol. IV, p 149. Sheldrick, G . M. 'System of Computing Programs", University of Cambridge, Cambridge, 1976 (adapted by Dr. C. Mealli). Dapporto, P.; Midollini, S.;Orlandini, A.; Sacconi, L. Inorg. Chem. 1976, 15, 2768.
2
In addition to the nucleophilic attack by hydride ion at the C 1 carbon atom site, other reactions may occur between 1 and nucleophiles. Indeed all manner of nucleophiles such as OH-,
4168 Inorganic Chemistry, Vol. 21, No. 12, I982
Bianchini, Meli, and Orlandini
Table 11. Positional and Thermal Parameters for [( t r i p h o s ) C ~ S ~ C O ] ~ atom
X
Y
z
u, A Z
c1 c2 c3 C4 C5 C6 C7 C8 C9 C10 C11 C12 C13 C14 C15 C16
535 (13) 851 (11) 2723 (22) 44 (6) 215 (10) 189 (11) 1990 (22) 29 (6) 787 (10) -306 (12) 1500 (23) 34 (7) -201 (10) 494(11) 848 (21) 34(7) 3105 (23) 46 (7) -192 (11) -218 (13) 825 (8) -1792 (8) 2491 (18) 58 (8) 1462 (8) -1681 (8) 2967 (18) 82 (10) 1684 (8) -2086 (8) 4045 (18) 82 (10) 1270 (8) -2603 (8) 4647 (18) 77 (9) 633 (8) -2714 (8) 4170 (18) 96 (11) 411 (8) -2309 (8) 3092 (18) 46 (7) 1162 (8) -1573 (7) -131 (15) 36 (7) 1741 (8) -1177 (7) -375 (15) 63 (8) 2197 (8) -1447 (7) -1279 (15) 96 (11) 2075 (8) -2113 (7) -1940 (15) 74 (10) 1496 (8) -2509 (7) - 1697 (15) 55 (8) C17 1040 (8) -2239 (7) -792 (15) 40 (7) C18 195 (10) -129 (8) -1697 (18) 38 (7) C19 521 (10) 530 (8) -2017 (18) 85 (10) C20 971 (10) 541 (8) -3047 (18) 111 (14) C21 1096 (10) -107 (8) -3758 (18) 99 (12) C22 770 (10) -767 (8) -3439 (18) 61 (8) C23 319 (10) -778 (8) -2408 (18) 37 (6) C24 -1115(8) 311 (9) -1292 (15) 40 (7) C25 -1255 (8) 1052 (9) -991 (15) 63 (9) C26 -1771 (8) 1418 (9) -1624 (15) 55 (8) C27 -2147 (8) 1042 (9) -2557 (15) 64 (8) C28 -2007 (8) 301 (9) -2858 (15) 72 (9) C29 -1491 (8) -65 (9) -2225 (15) 60 (8) C30 -1048 (6) -1465 (8) 3749 (14) 38 (7) C31 -779 (6) -1420 (8) 5003 (14) 42 (7) C32 -940 (6) -1953 (8) 5942 (14) 66 (8) C33 -1370 (6) -2533 (8) 5627 (14) 67 (8) C34 -1639 (6) -2578 (8) 4373 (14) 64 (8) C35 -1478 (6) -2044 (8) 3434 (14) 52 (7) C36 -1562 (7) -190 (8) 2507 (14) 30 (6) C37 -1693(7) 188 (8) 3670 (14) 44 (7) C38 -2222(7) 683 (8) 3740 (14) 55 (8) 799 (8) 2645 (14) 39 (6) C39 -2620 (7) C40 -2489 (7) 421 (8) 1482 (14) 70 (10) C41 -1960(7) -74 (8) 1412 (14) 47 (8) C -1304 (14) -2526 (15) -201 (27) 65 (9) 0 1681 (10) -3073 (11) -443 (23) 97 (7) Coordinates are multiplied b y lo4;temperature factors, by io3.
Y" Figure 2. Perspective view of the complex molecule [(triphos)Co(S,CO)] (ORTEP drawing with 30% probability ellipsoids). Table 111. Selected Bond Distances (A) and Angles (Deg) for [ (triphos)Co(S,CO)]
co-P1 co-P2 CO-P3 co-s1 co-s2 PIX3 P146 Pl-Cl2 P2-C4 Pl-CO-P2 Pl-Co-P3 Pl-CO-Sl Pl-cO-S2 P2-Co-P3 P2-Co-Sl P2Co-S2 P3-Co-Sl P3-CO-S2 Sl-cO-S2 Co-P1-C3 CO-PI-C~ Co-PlC12 C3-Pl-C6 C3-Pl-Cl2 C6-PI-Cl2 Co-P2-C4
2.246 (6) 2.259 (6) 2.271 (8) 2.260 (7) 2.250 (6) 1.85 (2) 1.84 (2) 1.84 (2) 1.83 (2) 89.0 (3) 91.6 (2) 165.6 (3) 93.5 (3) 91.6 (3) 97.2 (3) 155.5 (4) 101.2 (3) 112.6 (3) 75.5 (3) 111.6 (7) 119.6 (5) 118.2 (5) 101.5 (9) 104.7 (8) 98.9 (8) 109.3 (7)
P2C18 P2-C24 P345 P3C30 P3C36 51-c 52-c
C-O co. ' *c C0-P2418 Co-P2C24 C4-P2-C18 C4-P2-C24 C18-P2424 Co-P3-C5 Co-P3-C30 Co-P3-C36 C5-P3-C30 C5-P3-C36 C3O-P3436 CO-Sl-C Co-S2-C S1C-O S2-C-0 Sl-C-S2 CO-C-0
1.81 (2) 1.87 (2) 1.87 (2) 1.82 (2) 1.85 (2) 1.70 (3) 1.69 (3) 1.27 (3) 2.77 (3) 113.4 (5) 123.5 (6) 107.6 (8) 102.4 (8) 99.1 (9) 110.6 (8) 118.2 ( 5 ) 120.7 (6) 104.2 (9) 100.2 (9) 100.4 (7) 87.3 (IO) 88.0 (IO) 124.7 (22) 126.2 (21) 109.1 (16) 176.3 (21)
RO-, S2-, RS-, and NR2- react with 1 to give red-violet solutions, but no products can be isolated. However, if oxygen is bubbled into these solutions, the color turns yellow-green and crystals of empirical formula [(triphos)Co(S,CO)] (3) are precipitated. Compound 3 is quite air stable and soluble in chlorinated solvents in which it is nonconducting. The room-temperature kerfis equal to 1.97 pBras expected for a low-spin d7 configuration. The electronic spectra, pratically identical both in the solid state and in 1,2-dichloroethane solution, show absorption maxima at 10000 (E = 318), 14800 (E = 333), 21 050 (E = 592), and 23 550 cm-' (E = 4148), and are fully comparable with those of distorted five-coordinate cobalt(I1) complexes with P3S2donor set.7 The I R spectrum in the C O stretching region has two bands as 1690 and 1600 cm-', which are indicative of a chelate dithiocarbonate ligand.6J6 The crystal and molecular structure of the complex molecule consists of monomeric units of [(triphos)Co(S,CO)], whose perspective view is given in Figure 2. Selected bond distances and angles are reported in Table 111. The metal atom is five-coordinated by the three phosphorus atoms of the triphos ligand and by the two sulfur atoms of the dithiocarbonate
ligand in a distorted square-pyramidal environment. The distortion from the limit geometry is evidenced by the values of the P1-Co-S1 and P2-Co-S2 bond angles, 165.6 (3) and 155.5 (4)O, respectively, instead of the ideal 1 8 0 O . The cobalt atom and the dithiocarbonate ligand are essentially coplanar, the maximum deviation from the least-squares plane being 0.03 A. The Co-P and the Co-S bond distances, averaging 2.259 (7) and 2.255 (5) A, respectively, fall in the usual range; a comparison with the corresponding values reported for the = [(etriphos)Co (S,C(H)PEt,)] (BPh,), c ~ m p l e x Co-P(av) ,~ 2.200 (3) and Co-S(av) = 2.19 (2) A, shows an increasing of the bond distances in the coordination sphere, which could be attributed to electronic factors (Co(I1) instead of Co (111)) as well as to steric arguments (phenyl groups in the place of ethylenic chains). However, a variety of triphos cobalt complexes with different ancillary ligands is reported, with Co-P bond distances falling in an extremely large range of va1~es.I~ Bond distances and angles within the S z C O unit well match the values in other dithiocarbonate complexes; the S-C (1.695 (5) A (average)) and C - O (1.27 (3) A) bond distances closely resemble those found in the K[Rh(S2CO)2(PMe2Ph)2].3H20'6
(16) Gould, R. 0.;Gunn, A. M.; Van der Hark, T. E. M. J . Chem. SOC., Dalton Trans. 1976, 1714.
(17) Ghilardi, C. A,; Mealli, C.; Midollihi, S.;Nefedov, V. I.; Orlandini, A,; Sacconi, L. Inorg. Chem. 1980, 19, 2454 and references therein.
Structure of [(triphos)Co(S,CO)] (1.72 A (average), 1.26 A (average)) as those reported in the dimeric [(Cp2V),(C0S2)] complex18 (1.726 A (average), 1.262 A), where the dithiocarbonate acts as tridentate bridging ligand. A comparison with the [Pt(S,CO)(PPh,),] compound,lg where the phosphine ligands are each trans to the sulfur atoms of the dithiolate group, shows some difference, the S-C (1.78 A (average)) and C-O (1.19 A) bond distances in the platinum complex reflecting a larger r-electron withdrawing of the phosphine ligands, allowed by the square-planar geometry. However, the S-C and C - O bond distances, in the presence compound, seem to suggest an overall electronic delocalization of the S 2 C 0 group. Dithiocarbonate complexes are quite rare since they cannot be obtained directly from the ligand, which is unstable to disproportionation. Most of them are prepared from the reaction of metal xanthates with phosphines.6J9 The mechanism for this reaction has been suggested to involve the formation of an ionized xanthate, followed by nucleophilic attack of this anion on the alkoxy group of the coordinated xanthate to give the dithiocarbonate complex and a xanthate ester.20 A similar scheme cannot be applied to the formation of 3. One, in fact, could think that, when 1 is treated with alkoxide, the RO- group may attack the coordinate Et,P.CS2 molecule to give the dithiocarbonate complex and phosphonium PR4+ cations. This does not happen both because the presence of molecular oxygen in the reaction mixture is mandatory and because 3 can be obtained by means of other non-oxygencontaining nucleophiles such as RS-, S2-,and NR2-. On the other hand, the dithiocarbonate complex 3 can be simply prepared by exposition in the air of a solution of 2. While at present no definitive conclusions are reached about the detailed mechanism and the role of oxygen in the formation of 3, it appears reasonable that a fundamental step is the nucleophilic attack on the -CS2 carbon atom to give products appropriate to substitutions at C l . An experimental confirmation of this is the synthesis of the trithiocarbonate complex [(triphos)Co(S,CS)] (4). This compound is obtained as red crystals from the reactions of 1 with alkoxides and elemental sulfur. It is air stable and soluble in common organic solvents in which it is nonconducting. The peffat room temperature equal to 2.10 pB is indicative of one unpaired spin. The IR spectrum is identical with that of the dithiocarbonate derivative 3 except in the C = O region, where (18) Pasquali, M.; Floriani, C.; Chiesi-Villa,A.; Guastini, A. J. Am. Chem. SOC.1980, 19,3847. (19) Lin, I. J. B.; Chen, H. W.; Fackler, J. P., Jr. Inorg. Chem. 1978, 17, 394. (20) Alison,J. M. C.; Stephenson,T. A. J. Chem. Soc., Dalron Trans. 1973, 254.
Inorganic Chemistry, Vol. 21, No. 12, 1982 4169
3 adsorbs and in the C=S region, where 4 shows bands at 1040 and 8 5 5 cm-', which can be compared with those reported for some v2-coordinated CS, complexes.21 The UV spectrum in 1,2-dichloroethane is fully comparable with that of 3, showing absorption maxima at 9700 (e = 458), 14 500 (e = 430), 18500 (e = 975), and 20850 cm-' (e = 1815). All the information gathered from the spectroscopic, magnetic, and conductivity measurements is suggestive of a distorted square-pyramidal coordination around the cobalt atom, the three phosphorus atoms of the triphos ligand and two sulfur atoms of the trithiocarbonate ligand serving as donor atoms.
4 It is noteworthy that trithiocarbonate complexes have been obtained on reaction of CS2 with metal carbonyl anions.22 Among the hypotheses about the formation of these products is included the presence of elemental sulfur released in some manner from CS2 in the reaction mixture. To our knowledge the detailed mechanism for these reactions is not yet understood. Electron withdrawal by the metal ion, besides facilitating attack by a nucleophile on the C1 carbon atom, can weaken the P-CS2 bond. Recently, in fact, it has been reported that both PEt, and CS2 complexes can be obtained by reaction of the Et3PCS2zwitterion with metal species.2!5 In this finding it is not completely surprising that 1 reacts with sodium to give the complex [(triphos)Co(r-CS2)] (5) recently prepared in this laboratory by a different reaction.23 However, it is interesting that, upon cleavage of the P-CS2 bond, the CS2 group rearranges to an v2 complex. This may open a new route to CS2 metal complex. Acknowledgment. We thank G. Scapacci and F. Cecconi for technical assistance and F. Nuzzi and G. Vignozzi for microanalyses. Registry No. 1, 83024-91-9; 2, 82585-02-2; 3, 82590-72-5; 4, 82307-22-0; 5, 14244-56-1. Supplementary Material Available: Table IV, containing the least-squares plane related to the CoS2C0 group, and a listing of structure factor amplitudes (7 pages). Ordering information is given on any current masthead page. (21) Coucouvanis, D. Prog. Inorg. Chem. 1979, 26, 402 and references
therein.
(22) Benson, I. B.; Hunt, J.; Knox, S.A. R.; Oliphant, V. J . Chem. SOC., Dalton Trans. 1978, 1240. (23) Bianchini, C.; Mealli, C.; Meli, A,; Orlandini, A,; Sacconi, L. Inorg. Chem. 1980, 19,2968.
